<?
function getMonday($weeknr)
{
$year = date('Y');
$offset = date('w', mktime(0,0,0,1,1,$year));
$offset = ($offset < 5) ? 1-$offset : 8-$offset;
$monday = mktime(0,0,0,1,1+$offset,$year);
return   strtotime('+' . ($weeknr - 1) . ' weeks', $monday);
}

function getFriday($weeknr)
{
$year = date('Y');
$offset = date('w', mktime(0,0,0,1,1,$year));
$offset = ($offset < 5) ? 1-$offset : 8-$offset;
$friday = mktime(0,0,0,1,5+$offset,$year);
return   strtotime('+' . ($weeknr - 1) . ' weeks', $friday);
}

echo date("d.m.",getMonday(date("W"))), ' - ' , date("d.m.",getFriday(date("W")));

?>